"... Our results show that the distribution of Habitable Zone outer boundaries generally lie within 0.5 AU of the host stars, but that this small cross-sectional area is counter-balanced by a relatively high rate of stellar close encounters that would disrupt planetary orbits within the Habitable Zone of typical Omega Centauri stars."

"The star 55 Cancri was one of the first known exoplanet hosts and each of the planets in this system is remarkable. Planets b and c are in a near 1:3 resonance. Planet d has a 14.5 year orbit, and is one of the longest known orbital periods for a gas giant planet. Planet e has a mass of 8 M? and transits this bright star, providing a unique case for modeling of the interior structure and atmospheric composition of an exoplanet. Planet f resides in the habitable zone of the star. If the planets are approximately co-planar, then by virtue of having one transiting planet, this is a system where the Doppler technique has essentially measured the true mass of the planets, rather than just Msin i. The unfolding history of planet discovery for this system provides a good example of the challenges and importance of understanding the star to understand the planets."

"...We find that the SO2−3 'light chemistry' is rapid enough to build up the prebiotic inventory for stars hotter than K5 (4400 K). We show how the abiogenesis zone overlaps with the liquid water habitable zone. Stars cooler than K5 may also drive the formation of these building blocks if they are very active...."

"...We develop a simple model for planetary growth including pebble and gas accretion, and orbital migration in an evolving protoplanetary disk. ... The model successfully reproduces the observed frequency and distribution of giant planets and brown dwarfs. The fit for super Earths is poorer for single-planet systems, but improves steadily when more protoplanets are included. Although the study was designed to match the extrasolar planet distribution, analogs of the Solar System form in 1-2% of systems that contain at least 4 protoplanets."

"... This Colloquium discusses how a multitude of physical factors act in tandem to regulate the propensity of worlds for hosting detectable biospheres. We focus primarily on planets around low-mass stars, as they are most readily accessible to searches for biosignatures. We discuss how factors such as stellar winds, the availability of ultraviolet and visible light, the surface water and land fractions, stellar flares and associated phenomena place stringent constraints of the potential evolution of life on these planets."

"... We find that 10 km-scale submoons can only survive around large (1000 km-scale) moons on wide-separation orbits. Tidal dissipation destabilizes the orbits of submoons around moons that are small or too close to their host planet; this is the case for most of the Solar System's moons. A handful of known moons are, however, capable of hosting long-lived submoons: Saturn's moons Titan and Iapetus, Jupiter's moon Callisto, and Earth's Moon...."

"... Because of weathering's integral role in the long-term carbonate-silicate cycle, we suggest that climate stability may be strongly affected by the anticipated rotational evolution of temperate terrestrial-type worlds, and should be considered a major factor in their study. In light of our results we argue that planetary rotation period is an important factor to consider when determining the habitability of terrestrial worlds."

"We propose that retinal-based phototrophy arose early in the evolution of life on Earth, profoundly impacting the development of photosynthesis and creating implications for the search for life beyond our planet. ... We propose a scenario where simple retinal-based light-harvesting systems like that of the purple chromoprotein bacteriorhodopsin, originally discovered in halophilic Archaea, may have dominated prior to the development of photosynthesis. We explore this hypothesis, termed the 'Purple Earth,' and discuss how retinal photopigments may serve as remote biosignatures for exoplanet research."

Abstract: There exists a positive correlation between orbital eccentricity and the average stellar flux that planets receive from their parent star. Often, though, it is assumed that the average equilibrium temperature would correspondingly increase with eccentricity. Here, we test this assumption by calculating and comparing analytic solutions for both the spatial and temporal averages of orbital distance, stellar flux, and equilibrium temperature. Our solutions show that the average equilibrium temperature of a planet, with a constant albedo, slowly decreases with eccentricity until converging to a value 90% that of a circular orbit. This might be the case for many types of planets (e.g., hot Jupiters); however, the actual equilibrium and surface temperature of planets also depend on orbital variations of albedo and greenhouse. Our results also have implications in understanding the climate, habitability, and the occurrence of potential Earth-like planets. For instance, it helps explain why the limits of the habitable zone for planets in highly elliptical orbits are wider than expected from the mean flux approximation, as shown by climate models.

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